Your steel spur gear is what caused it to strip out the clutch bell. Watch out new series on the T-Maxx and you will hear me complain about that steel spur on many occasions. Get a plastic one, way cheaper in the long run.
As for not shifting, one of two things (or three if you count the stripped out clutch bell lol). First, your grub screw is too tight. Make sure you are adjusting the shift point and not the grub screw for the shaft, they are very close to each other. Second could be the dog is not slinging out because it's dirty. And a legit third would be that shaft grub screw. If you backed it out, the shaft will just spin and it will never shift. Instead it will chew up the aluminum piece on the shaft. I would check it by pulling it out of the trans.